We have talked briefly about what he would do if I asked him not to date her at all. He said he might date her anyway.
This bothers me.
How is he ADDING to your sense of security by telling you he's going to ignore you and your discomfort and go on to get his jollies anyway? It seems dismissive/ inconsiderate. No wonder you don't feel stable. He doesn't help create emotionally safe space for you.
How long have you all been together anyway?
Say he plunges on and guess what? You like her. Nothing horrible happens. You might end up liking your meta fine.
Except... he plunged on without taking your concerns seriously.
You end up feeling like he's not trustworthy. This makes him a great polypartner HOW?
The ends wouldn't justify the means. Sigh.
One of the things we said in our relationship is no rules no stipulations. Only be considerate and exercise communication and protection.
How is him being willing to ignore your discomfort him being considerate, communicative and protective of you or of trust you share between you?
In any ol' way?
He wants the freedom to invest in any type of relationship he wants.
Or while maintaining your trust, goodwill and blessing?
If him starting a relationship with her means his relationship with you is still solid and stable, that is one thing.
If him starting a relationship with her means his relationship with you is in the toilet -- that's another.
Is he going all "kid in the candy store" or something?
- ASK what he plans to to to continue to nurture/cultivate his relationship with you while dates the other person.
- ASK if he is willing to meet your needs in this transitional time to help make the transition easier on you.
If he's not giving you a yummy sounding offer/promise? If he is not willing/able to meet your needs? Could not agree to participate in polyship with him this way.
Disappointing maybe, but straight up and you can move on from there. That's better than endless run around!
I am sorry you are dealing in this.